1. Field of the Invention
The present invention relates to a track fixing structure for fixing a track rail to a prescribed base, such as the bed of a machine tool, and a linear motion equipped with said fixing structure.
2. Description of the Prior Art
Heretofore, fixing of a track rail equipped on a linear motion guide unit was normally performed by forming a plurality of bolt insertion holes along the lengthwise direction of the track rail itself, and fastening by screwing bolts inserted into each of said bolt insertion holes into the bed of a machine tool and so forth. However, in this fixing method, due to deformation of the vicinity of the above-mentioned bolt insertion holes of the track rail caused by fastening of the bolts, waviness formed in the track rail thus preventing the track rail from being straight.
A known example of a fixing structure that solves this problem is shown in FIG. 1. Furthermore, said fixing structure is disclosed in Utility Model Laid-Open Publication No. 4-70437, and said publication discloses an example that is used for fixing a track rail of a linear motion rolling guide unit.
As shown in the drawing, said linear motion rolling guide unit is equipped with track rail 1, in which two track grooves 1a each are formed along the lengthwise direction on the left and right sides, a slider in the form of sliding unit 3 able to move relative to track rail 1 and in which rolling element circulating path 2 is formed corresponding to these track grooves 1a, and a large number of balls 4 arranged and contained within rolling element circulating path 2 that bear the load by circulating while rolling over the above-mentioned track grooves 1a accompanying movement of sliding unit 3.
Flange 1d, having tapered surface 1c for its upper surface, which gradually widens towards bottom mounting surface 1b, is formed on both sides of the bottom portion of track rail 1. Said track rail 1 is placed on bottom surface 5b, namely a reference surface, of groove 5a, having a roughly rectangular cross-section, formed in a prescribed base 5, such as the bed of a machine tool.
A pair of clamping members 6 and 7 are provided within the above-mentioned groove 5a so as to sandwich track rail 1 from both sides, and are fastened to base 5 by bolts 8.
Contact surfaces 6a and 7a are formed in each of the outsides of both clamping members 6 and 7. Together with these making contact with reference surfaces in the form of both left and right inside surfaces 5c and 5d of the above-mentioned groove 5a, tapered surfaces 6b and 7b, which make contact with tapered surfaces 1c of track rail 1, are formed on the insides.
In the fixing structure of the above-mentioned construction, tightening of bolts 8 results in the formation of wedging action by track rail 1 and both clamping members 6 and 7 on both tapered surfaces, thereby resulting in positioning and fixing of track rail 1.
In the construction of the prior art as described above, the tightening force for bolts 8 is applied to track rail 1 through clamping members 6 and 7.
In said construction, although the straightness of track rail 1 in the vertical direction can be obtained at a high level by the action of a reference surface in the form of bottom surface 5b of groove 5a, since positioning in the horizontal direction is performed only by the frictional engagement of track rail 1 and each tapered surface of clamping members 6 and 7, said positioning is relatively unstable. Since force in the horizontal direction becomes locally strong at the locations of bolts 8, waviness forms in track rail 1 in the horizontal direction, thus resulting in the disadvantage of it being difficult to improve straightness in said horizontal direction.